An electricity-generating device using a permanent magnet power generator as a small and medium-sized power generator and using a wind turbine or a water turbine as an energy source is attracting attention. FIG. 7 shows a single connection diagram of a water-turbine electricity-generating device using the permanent magnet power generator, and the water-turbine electricity-generating device is interconnected to an electric power system 6 through an interconnection transformer 5. In FIG. 7, Numeral 1 denotes a water turbine, numeral 2 denotes a flywheel and numeral 3 denotes a permanent magnet power generator, which are coupled through bearings 4.
Numeral 10 denotes a converter panel, and the converter panel is equipped with respective components including a first converter (inverter) 11, a second converter 12, a brake circuit for regenerative braking 13, a smoothing capacitor 14, a filter unit 15, electromagnetic switches 16, 17, and a breaker 18. Numeral 20 denotes a generator panel, which has a breaker 21 performing interconnection control with respect to the electric power system 6. Numeral 30 denotes a dummy resistor device, in which plural resistors 33 having different resistance values are connected through breakers 31 and electromagnetic switches 32 respectively.
Numeral 40 denotes an upper control unit, and the control unit 40 inputs rotation signals of the permanent magnet power generator 3 detected by an encoder through the converter panel 10. The control unit 40 also outputs control commands such as an output of a speed command to the converter panel 10, an output of a valve-position command to an inlet valve 1a of the water turbine and an output of an input command to the dummy resistor device 30. The electricity-generating device using the permanent magnet power generator shown in FIG. 1 is publicly known by, for example, Patent Publication 1 and so on.
When the electricity-generating device shown in FIG. 7 is interconnected to the electric power system 6, the breaker 21 is turned on by outputting an interconnection/operation command from the generator panel 20, then, the breaker 18 and the electromagnetic switch 17 are turned on in the converter panel 10, thereby converting alternate current from the electric power system 6 into direct current by the converter 12 to charge the smoothing capacitor 14. The input command is outputted to the electromagnetic switch 16 at a point when the initial charge of the smoothing capacitor 14 is performed and the preparation for operation is completed. The control unit 40 also outputs the speed command and a power factor command to the inverter 11 to operate the inverter 11, controlling the permanent magnet power generator 3 within an interconnection operation range to which dotted lines are given shown in FIG. 8.
In FIG. 8, the vertical axis indicates the shaft input of the permanent magnet power generator and the horizontal axis indicates the rotational speed. When a rated capacity is f0, interconnection operation is performed while speeds n1, n2 around a rated speed n0 form the operation range of the permanent magnet power generator.
When an abnormality occurs in the system interconnection during the interconnection operation, the operation of the converter 12 is stopped and a switching device 19 of the braking circuit 13 for regenerative control is turned on, thereby allowing electric current to flow in a regenerative resistor 19′ and consuming the energy.
In the case where the small and medium-scaled electricity-generating device is operated by being interconnected to the electric power system, there may be a case where it is difficult to realize system interconnection when some kind of abnormality occurs in the electric power system as an interconnect destination. Even when a sufficient wind volume is secured in wind power generation and when a sufficient water volume is secured in water power generation, that is, even when energy for generating power is sufficient in both cases, the interconnecting electricity-generating device has to be stopped when the autonomous operation function is not provided. It is needless to say that the autonomous operation can be realized by specially adding the dummy resistor device or a high-speed guide vane control unit by an electric servo motor and so on to the electricity-generating device. However, it is necessary to add a peculiar operation function in that case, which is disadvantageous in aspects of an installation place and costs.